I think it's Netbird with their reverse proxy feature.
https://docs.netbird.io/manage/reverse-proxy
Netbird is like Tailscale, but Open Source. You don't have to self-host, but you can. They have a reverse proxy feature that let's you easily expose a device to the Internet. You can set basic authentication on the service, like requiring a password to access the page or only allowing certain IPs to access the page.
I use this with my parents. I got tired of the Tailscale app on the Google TV constantly shutting down. With the reverse proxy, there's no more VPN app. My service is publicly accessible, but protected by an IP allow list.